Thanks for all the comments (more on Flickr and Facebook!)

This was my first attempt (from last night before getting your comments) at mixing greys using all kinds of combinations of burnt sienna and phthalo blue – adding perm rose or lemon yellow and also trying with some indigo. N one of these achieved the grey colour which I use a lot (and which is so easily mixed with Burnt Sienna and French Ultramarine.)

I will experiment further but I DO need to be able to mix a good neutral grey quickly and consistently.